The current project is a continuation of research done on cerebral arterial disorders. The experimental model was one of the Rhesus monkey in which vasospasm can be induced in the intracranial arteries by the application of blood, or in some instances, catecholamine or serotonine- like substances. It has been found that such cerebrovasospasm can be alleviated by the application of alpha blocking agents to the C.S.F. pathways bathing the intracranial vessels. The present work is a continuation on the original work and consists of two major phases: (1) An evaluation of the changes in cerebral blood flow related to the degree and extensiveness of intracranial arterial spasm. The experimental model for this study is a Rhesus monkey in which only one major vessel remains supplying the cerebral circulation. The spasm is induced by the application of blood and a flow probe around this remaining vessel detects changes in cerebral blood flow. (2) This second portion of the project is related to an evaluation of the dose and route of application of alpha blocking agents in order to alleviate cerebrovasospasm. Two major routes are being evaluated. The application of this substance, Dibenzyline, to the subarachnoid space and arteriographic follow up to demonstrate the presence and remission of cerebrovasospasm, and intravascular routes of administering the substance with a similar arteriographic evaluation. By utilizing the latter technique it is hoped to develop a clinically applicable means of delivering this drug in cases of cerebrovasospasm following aneurysm surgery or subarachnoid hemorrhage.